This study will attempt to investigate the secretory response of Growth Hormone in two groups of closely matched amenorrheic and eumenorrheic athletes following an acute bout of exercise and throughout the night. The two groups will undergo preliminary screening, basal blood work, Max VO2 determination and hydostatic weighing prior to the secretory study. Each subject will perform exercise at 70% Max VO2 for 50 minutes during which time blood will be drawn every ten minutes, and then every 5 minutes for 20 minutes post-exercise.